Fig. 4.

Successful knockdown of growth differentiation factor 15 (GDF15) in well-differentiated human primary airway epithelial cells. Normal human bronchial epithelial cells transduced with lentiviruses encoding human GDF15 shRNA (shGDF15) or control shRNA (shControl) were grown at air-liquid interface for 28 days to examine GDF15 expression. A: GDF15 mRNA levels were measured by quantitative real-time RT-PCR and normalized to GAPDH mRNA levels via the ΔΔCt method. B: GDF15 protein levels in basolateral supernatants were assessed by ELISA. C, top: quantitative Western blot densitometry data of GDF15 and GAPDH protein (loading control). C, bottom: representative Western blot pictures. Data are presented as means ± SE from 4 independent experiments. **P < 0.01, ***P < 0.001.